Useful Topics on Java

java_topic_list

#1 201 Core Java Interview Questions (** this 200 will cover the maximum topics)
https://www.javatpoint.com/corejava-interview-questions

#2 String
  a. String in basic 
    - https://www.javatpoint.com/java-string   
  b. String vs StringBuilder vs StringBuffer
    - https://www.geeksforgeeks.org/g-fact-27-string-vs-stringbuilder-vs-stringbuffer/
    - http://javarevisited.blogspot.com/2011/07/string-vs-stringbuffer-vs-stringbuilder.html
    - https://www.journaldev.com/538/string-vs-stringbuffer-vs-stringbuilder
  c. StringJoiner in Java8
  d. When to use StringJoiner over StringBuilder?
  e. Swap two Strings without using third variable 
  f. Searching characters and substring in a String
  g. Reverse a string in Java (5 Different Ways)
  h. Remove Trailing Zeros From String in Java  
  i. Why String is immutable in java ?
     -https://www.programcreek.com/2013/04/why-string-is-immutable-in-java/
     -https://stackoverflow.com/questions/1552301/immutability-of-strings-in-java    
  j. What is java String pool ?
     - https://www.journaldev.com/797/what-is-java-string-pool
        
  # Collection
    a. Overview
      - https://www.edureka.co/blog/java-collections/
      - https://dzone.com/articles/an-introduction-to-the-java-collections-framework
    b. Array vs ArrayList
    c. HashMap vs Hashtable
    d. Comparable and Comparator
    e. hashCode() and equals()

There is a large number of elementary algorithmic interview questions you can use with any language (memory addressing, networking, trees, hash tables, sorts, concurrency, etc), but if you're looking for Java-specific questions, here are a few, in no particular order of difficulty or relevancy...Java Interview Question